Stabilized polyamides

ABSTRACT

A HIGH MOLECULAR WEIGHT FIBER-FORMING STABILIZED POLYAMIDE CONTAINS 5-100 P.P.M. BY WEIGHT ON THE POLYAMIDE OF PHOSPHORUS IN THE FORM OF A PHOSPHOROUS ACID OR A SALT THEREOF AND 100-10,000 P.P.M. BY WEIGHT ON THE POLYAMIDE OF A SULFUR-CONTAINING PHENOL HAVING THE FORMULA OH-$-S-R WHERE $ REPRESENTS A BENZENE RING. THE HYDROXYL GROUP IS POSITIONED PARA OR ORTHO TO THE SULFUR ATOM AND R IS ALKYL, ARYL AND PREFERABLY AN IDENTICAL $-OH STRUCTURE AS ABOVE, LOCATED SYMMETRICALLY ABOUT THE SULFUR ATOM.

United States Patent 3,640,948 STABILIZED POLYAMIDES John Ernest Jackson, Pontypool, England, assignor to Imperial Chemical Industries Limited, London, England No Drawing. Filed Apr. 23, 1969, Ser. No. 818,787 Claims priority, application Great Britain, May 14, 1968, 22,886/ 68 Int. Cl. C08g 51/56, 51/62 US. Cl. 260-45.75 R 9 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to the stabilisation of high molecular weight fibre-forming synthetic linear polyamides or copolyamides against impairment of their properties by the action of heat and oxygen and by light, particularly when said polyamides are pigmented with titanium dioxide.

Synthetic linear polyamides and copolyamides, e.g. polyhexamethylene adipamide, are widely used in the manufacture of textile and other products, for instance yarns and fabrics. Such products are noted for their at tractive properties, such as great strength, i.e. high tenacity. Prolonged exposure to light, however, as in the case of curtains hung at windows, gradually impairs the properties of such polymers. In order to stabilise said polymers against light deterioration, small quantities of various manganese salts may be incorporated into the polymer during manufacture, but these often tend to cause discolouration on bleaching. The addition of a reducing phosphorus oxyacid or a salt thereof, called hereinafter a reducing phosphorus compound, reduces such discolouration.

Said polymers are also apt to be discoloured and degraded by heat in the presence of oxygen, for instance, during conventional heat setting processes. Heat stability, with or without manganese present, can be greatly improved by the addition of a suitable phenol e.g. 1,1,3-tris- (1-hydroxy-3-methyl-6-tertbutylphenyl)butane along with a suitable reducing phosphorus compound.

Polymer instability tends to increase with increasing content of many pigments, for instance, with increasing tiania content. Amounts of pigments such as titania, of the order of several percent, may be added in some cases and such instabilty may be come considerably exacerbated.

A free phosphorus acid or an inorganic salt thereof may be employed as the reducing phosphorus compound but inorganic ions have a tendency to promote aggregation of the titania particles and impair the quality of the titania dispersion. Impairment of the titania dispersion clearly has a more disadvantageous effect the higher the amount of titania incorporated in the polymer. Addition of organic reducing phosphorus compounds such as amine salts, on the other hand, while reducing the difficulties associated with dispersion of the titania, may give rise to difliculties in the yarn drawing process, such as formation of undesirable deposits on the apparatus.

Hence it is of considerable advantage to be able to reduce the addition of such reducing phosphorus com "ice pounds, both inorganic and organic, to a minimum amount consistent with obtaining the desired effect of such addition.

In practice hitherto it has been found that the said reducing phosphorus compounds must be present in an amount equivalent to approximately 200 p.p.m. of phosphorus in the polymer, or considerably above this figure, for them to exert any appreciable effect. Applicants have now found that the addition of a phenolic antioxidant containing sulphur at a suitable position in its molecule, in conjunction with a reducing phosphorus compound, permits the addition of much smaller amounts of said phosphorus compound, thus overcoming the aforesaid disadvantages, while at the same time, surprisingly, at least preserving the advantages stabilising effect.

The sulphur-cointaining phenols used in the present invention have the general formula OHS.R, where represents a benzene ring, with the OH group positioned paraor orthoto the sulphur atom, and R may be an alkyl or aryl group and preferably an identical OH structure located symmetrically about the S atom. Hydrogen atoms of the benzene ring or rings may be substituted by aryl or alkyl groups such as methyl, ethyl, tertiary butyl and the like; again, if there are two benzene rings, preferably symmetrically about the S atom. Whilst the hydroxyl group or groups may be positioned either paraor orthoto the sulphur atom in said sulphur containing phenols, para-positioning is preferred.

A further advantage of compositions according to the present invention is that formation of gel, for instance, during melt spinning, such as may occur by degradation of the molten polyamide or copolyamide in the presence of. pigments such as carbon black, is hindered. Furthermore the loss of amine ends when, for example, a polyamide fabric is submitted to a process of conventional heat setting, is markedly reduced. This aspect is of particular importance since such loss of amine ends is apt to give rise to stripiness in such a fabric when dyed.

The amounts of phosphorus, sulphur-containing phenol, and manganese (when added), based on the polymer in weight proportion, used in carrying out the present invention, are as follows:

Phosphorus (introduced in the form of a reducing phosphorus compound): 5 to parts per million and preferably between 50 and 100 parts per million.

Sulphur-containing phenol: from 100 to 10,000 ppm. and preferably from 400 to 1,000 parts per million.

Manganese (optionally introduced, in the form of an oxide, hydroxide or salt): from 5 to 1,000 parts per million and preferably from 10 to 100 parts per million.

The present invention accordingly comprises in one of its aspects a high molecular weight fibre-forming synthetic polyamide or 'copolyamide in which there have been incorporated from 5 to 100 parts per million parts by weight on the polyamide of phosphorus in the form of a phosphorous acid or a salt thereof and 100 to 10,000 parts per million by weight on the polyamide of a. sulphur-containing phenol having the general formula OH.S.R, where 4 represents a benzene ring, 'With the hydroxyl group positioned paraor orthoto the sulphur atom, R being an alkyl or aryl group, and preferably an identical OH structure as above located symmetrically about said sulphur atom.

As already indicated, the invention is particularly adapted to polyamides containing titania or other pigments, and is applicable to both acid-stabilised and basestabilised polyamides.

Conventional adjuvants may also be added to the polyamides at any convenient stage in their manufacture, for instance: dyes, pigments, dyestuif-for-rners, plasticisers or resins.

The invention includes shaped articles of the above high molecular weight linear polyamides containing phosphorus, a suitable sulphur-containing phenol and optionally manganese, such as, for example, fibres, fila- 4 The reducing phosphorous compounds which may be added include ortho phosphorous, meta phosphorous, pyro-phosphorous and hypo-phosphorous acids, and also thiophosphorous acids, e.g. dithio-orthophosphorous acid,

merits, yarns, films, fabrics and other textile materials. 5 and their organic and inonganic salts.

The reducing phosphorus acid or salt thereof and the Exam l f h organic salts are; sulphur-containing phenol may be incorporated in the polyamide by addition at any suitable stage in its manufi g i i 3 5331 hcfiehyphophosphlte facture. Preferably they are mixed with the polyamide 9 gf p starting materials before the polymerisation commences. f' i or 9 1 e hos bite Alternatively, they may be added to the finished poly- {at ano ammqmum ypop triethyla-mmonium hypophosphite amide, for instance by dusting them on to the polyamide triphenyl orthophosphite chip prior to its melting. When titanta is added, an intn 1 t h soluble manganese salt or a hydroxide or oxide or other 1 aury n lop osp 1 e compound thereof may, if required, be precipitated pre- 15 The following examples, in which the parts are parts viously thereon so as to coat the titania particles. by weight, are intended toillustrate, but not to limit,

The stabilising components of the present invention the invention. may be added, either separately or in combination, at EXAMPLES 1 AND 2 suitable points in a continuous polymerisation process, such as that carried out in a pipe or coil, In thi case 6.6 nylon was prepared by the conventional method, the sulphur-containing phenol is preferably added as a from heXamethylem? dlamine and lp q acld, Wlth the solution in aqueous caprolactam and the titania added addition, at the beglllfllng 0t polymerlsatlqnt of a Slurry as a slurry. containing titanium dioxide pre-coated with manganese Use of the sulphur-containing phenols of the present P P The titanium diox'lde was added Such invention in a continuous polymerisation process presamount that theTe WaS pp t y 2% 0t It In the cuts a surprising advantage in reducing the formation of final p y SOdlUm hy p pl Was also addfid at deposits in the polymerisation apparatus and its appended the Sa e e in n amount equlvalent to 70 Parts P apparatus, thus permitting operation of such apparatus million of Phosphorus on the P y Producedfor long periods. In Example 1 there was further added 0.05% (on Examples of the high molecular Weight linear polyp ly r) of 1,1,3-tr1$ Y Y- y y amides (which expression is to be understood as inp y butane, a Phenol not contalmng P and cluding copolyamides) are listed below. which is known to be a very efficient antioxidant for polyamides. In examples 2 there was added 0.5% (on POLYAMIDE polymer) of bis(2-methyl-4-hydroxy-S-tert-butyl phenol) polyhexamethylene sebacamide sulphide. polyhexamethylene adipamide 200 denier, 20-filament yarns were melt spun from polyoctamethylene adipamide the polymers produced in each case and drawn to 70 polydecamethylene sebacamide denier. Before drawing, samples of said yarns, free of polypentamethylene sebacamide finish, were tested for amine end group content (called polydodecamethylene adipamide AEG) and relative viscosity (R.V.) in the conventional poly-epsilon-caprolactam manner, as well as for whiteness. The whiteness of the poly-omega-aminoundecanoic acid yarn was measured in terms of b chromaticity on a poly-m-xylylene adipamide Mecco Colormaster Mark V colorimeter, .(obtainable polyhexamethylene isophthalamide from Manufacturers Engineering & Equipment Corpgra;

tion, Warrington, Pa., USA.) using t e rotating is gfig g i s ggg g ggif followmg starting maassembly. The colorimeter was pre-calibrated. Perfect y whiteness was denoted by a value of 0.333. The yarns (1) hexamethylene diammonium adipate and epsilonwere then heated in air at 220 C. for 30 seconds and the caprolactam above mentioned tests again carried out. (2) hexamethylene diammonium adipate and hexa- The results obtained, together with the changes in said methylene diammoniumsebacate, properties are shown in the table below.

TABLE 1 EFFECT OF HEATING EXPERIMENTAL YARNS FOR 30 SECONDS AT 220 0.

Initial analysis Final analysis Change in analysis [lb], lib) A Ex- A.E.G., chroma- A.E.G., chroma- A.E.G., ample Additives equ.ll0 g. ticity (b) equ./10 g ticity (b) equ./l0g. Ah

1 2% titania, 26 p.p.m. Mn, 0.05% 1,1,3-tris (1-hydroxy-3-methy1-6-tert 47.2 0.323 29.4 0.285 17.8 0.038 butyl phenyl) butane and p.p.n1. P as sodium hypophosphite. 0. 038 2% titania, 26 p.p.m. Mn, 0.5% bis (2-methyl-4-hydroxy-5-tert. butyl 4.44 0. 323 37.2 0 300 7. 2 0. 018

phenyl) sulphide and 70 p.p.m. P as sodium hypophosphite.

(3) hexamethylenediammoniumadipateandhexamethylenediammoniumisophthalate,

(4) hexamethylene diammonium terephthalate and dodecamethylene diammonium. terephthalate,

(5) the salts from hexamethylene diamine, adipic acid and 1,4-diphenyl adipic acid.

Suitable manganese salts, if required, are, for instance the lactate, acetate, formate, stearate, ortho-phosphate and pyrophosphate.

It can be seen that with only 70 ppm. of phosphorus present the yarn containing bis (2-methyl-4-hydroxy-5- tert. butyl-phenyl) sulphide was very much more stable than the containing 1,1,3-tris (l-hydroxy-3-rnethyl-6- tert butyl phenyl) butane, even though this compound is well known to be very efiicient antioxidant, as aforesaid, and that the b chromaticity remained at as high a value as 0.300. With the aforesaid very low phosphorus content there was no trouble with the titania dispersion even though the titania content of the polymer was as high as 2%.

EXAMPLES 3 AND 4 Examples 1 and 2 were repeated using titania with no not possible to run a trouble-free process for anything like two weeks, owing to deposits forming in the apparatus. Thus, the use of his (2-methyl-4-hydroxy-5-tert. butyl phenyl) sulphide gave a surprising advantage, permitting operation of the continuous process over long Mn. present. The results are shown in table 2 below. 5 period,

TABLE 2 Initial analysis Final analysis Change in analysis 1, u A Ex- A.E.G., chroma- A.E.G., chroma- A.E.G., ample Additives equ./g. ticity (b) equ./10 g. tieity (b) equ./10g. Ab 1 2 7g 5% )(rg: g ag tggs v ig ggi s 1 l y gggg a ng'ethyl s tert.buty1 49. 3 0. 324 33.8 0. 284 15. 5 0. 040 2 2 7ggngnlgnb) 9(82331149315112512132.hydroxy-5-tert;.butyl phenyl) 40. 9 0. 325 37. 2 0. 308 3. 7 0. 017

I EXAMPLES 5 and 6 EXAMPLES 7 and 8 40 denier 13 filament yarn containing 0.3% titania Examples 5 and 6 were repeated but with 80 p.p.m. was spun for two weeks at 7.7 lb./hr. from a 10 1b./hr. phosphorus. The diflFerence, before and after heating, capacity continuous polymerization apparatus. in results of the oxidation test described in Examples a Titania was injected as a slurry at the 70% injection and 2 are shown in Table 3 below. point i.e. at a point 70% along the length of the evaporating section previous to the polymerization zone. TABLE 3 In Example 5, bis (2-methyl-4-hydroxy-5-tert butyl phenyl) sulphide was injected as an approximately 1% 235 Additive B M solution in approximately 50% w./w. aqueous caprolactam at the point, to give a level of approximately '52251?fifilfi 1M 0 -()5%'i11 the yarn, 8 Bis (Z-methyM-hydroxy-fitert. butyl 11.5 0.039

/ 50 p.p.m. of phosphorus as hexamethylene diamine 30 phenynsllphide' hypophosphite were added along with the hexamethylene diamine at the entr to the apparatus.

During the two w eeks spinning, extrusion performance EXAMPLES 9*25 was generally good and yarn lustre was well within ac- 6.6 nylon was prepared by the conventional method, ceptable limits; the fault rate was only 5 breaks and l from hexamethylene diamine and adipic acid, with addifilament break per 100 lbs. The yarn was drawn on a tion of TiO pigment, various phosphorus compounds conventional Rieter drawtwist machine at 3,300 f.p.rn. and various antioxidants as shown in Table 4. (AFN (2) There were no undesirable deposits formed on the drawis a titania coated with an Mn compound, 2% of which ing apparatus, even after 7 days continuous drawing. introduces 26 p.p.m. Mn into the polymer melt).

The drawn yarn was tested on a laboratory oxidation The spun yarn was tested for relative viscosity, amine testing apparatus, as in Examples 1 and 2, and was end group content (A.E.G.), carboxyl end group content shown to have a final b-chromaticity of 0.291. (C.E.G.) and total end group content (T.E.G.). The

The procedure of Example 6 was the same as that for T.E.G. is a measure of chain scission and decomposition Example 5 except that 1,1,3-tris (l-hydroxy-3-methyl-6- and is found from a calibration curve with RV. After tert butyl phenyl) butane was used instead of his (2- heating for 30 seconds at 220 C. the yarns were again methyl-4-hydroxy-5-tert butyl phenyl) sulphide. In this subjected to the measurements. The differences in the case the final b chromaticity was only 0.281 and it was results before and after heating are shown in Table 4.

TABLE 4.

Effect of heating undrwwn 220/20 denier finish-free yarn for 30 seconds at 220 C.

Change in analysis Ex- -A A.E.G., A C.E.G., A chromaample Additives equ./10 g. equ.l10 g. T.E.G. ticity 7 2% AFN (2) T102 18.4 12 94 0.045 2% AFN (2) T102 plus 75 p.p.m. P as NaH2P02 21. 2 13 84 O. 047 2%NAlg2) and 0.05% 2,2,1-methylene bis(4 methyl-5 t. butylphenol) and 75 p.p.m. P as 31. 5 11 0. 047

a 2 2. 10 2% AFN (2) and 0.05% 1,3,5 trimethyl-2,4,6-tris (3,5 di 1;. butyl-4 hydroxy benzyl) benzene and 17. 5 7 92 0. 047

p.p.m. P as NaH2PO 11 2% AFN I$2) agd 3 methyl-6 t. butylphenol and crotonaldehyde condensate and 75 19. 2 11 96 0. 046

.p.m. as a g 12 2751355115?) (and 0.025% bis (2 methyl-4-hydroxy-5-t.-butyl phenyl) sulphide and 75 p.p.m. P 14. 9 10 59 0. 040

as a 2 2- 13.- 2% AlerfigI (goand 0.05% bis(2 methyl-'i-hydroxy-5-t.-buty1phenyl) sulphide and 75 p.p.m. P 8. 5 1 11 0. 025

as a 2 2- 14.... 2% AI ]IE[(2P) (and 0.075% bls(2 methyl--hydroxy-5-t.-butyl phenyl) sulphide and 75 p.p.m. P 2. 1 3 12 0. 030

as a 2 2- 15 2% (2) and 0.1% bis(2 methyL4-hydroxy-5-t-butyl phenyl) sulphide and 75 p.p.m. P 9. 2 1 7 0. 031

as a 2 z- 16 2% AFN (2) and 0.05% bis(2 methyl-4-hydroxy'5-t.-butyl phenyl) sulphide and 75 p.p.m. 9.2 5 4 0.026

P as H.M.D. hypophosphite. 17 2% APILN (12) ard00.05% bis (2 methyl-4-hydroxy-5-t.-buty1phenyl) sulphide and 75 p.p.m. P 10. 2 7 36 0. 036

as use are 1 18 2% Afilifif apd 0.05% bis(2 methyl-4-hydroxy-5-t.-butyl phenyl) sulphide and 75 p.p.m. P 10. 0 2 16 0. 027

as n 2 2 2' 19 2% 115511101) an)d 0.05% bis (2 methyl4-hydroxy-5-t.-butyl phenyl) sulphide and 75 p.p.m. P 10. 3 1 14 0. 029

as a 2 2 2. 20 2% APFIEII (12 Oand 0.05% bis(3-t. butyl-4-hydroxy-5-methyl phenyl) sulphide and 75 p.p.m. P 12.0 4 20 0. 036

as a 2 2. 21 2% Agikqggnd 0.05% bis(3 methyl-4-hydroxy 5-t.butyl benzyl) sulphide and 75 p.p.m. P 16. 2 8 38 0. 014

as a 2 2. 2% AFN (2) and 0.05% 2.2-thio-bis(4 methyl 6-t. butyl phenol) and 75 p.p.m. P as NaHrPOz- 12. 6 7 40 0. 035 2% AFN (2) and 0.05% 2,2,thlo-bis (3 methyl-4,6 di tert. butylphenol) and 75 p.p.m. P as 13.2 8 45 0.036

It is clear, particularly when the results obtained with 0.05% of the antioxidant are compared, that there was less change in the properties with the yarn containing the antioxidants of the present invention than there was with yarns containing the sulphurless antioxidants or with those containing no antioxidant. A difference of .002 in the value of the b chromaticity is visible to the naked eye.

Thus, it is clear that yarns containing the antioxidants of the present invention are more stable than those containing other antioxidants in equivalent amount.

What I claim is:

1. A high molecular weight fibre-forming synthetic polyamide wherein the improvement consists in that there have been incorporated from to 100 parts per million parts by Weight on the polyamide of phosphorus in the form of a phosphorous compound selected from the group consisting of phosphorous acid, thiophosphorous acid, hyphosphorous acid, an alkyl or aryl ester of one of said acids, an amine salt of one of said acids and a salt of one of said acids with an alkali metal, alkaline earth metal or manganese, and 100 to 10,000 parts per million by weight on the polyamide of a sulphur-containing phenol having the formula M OH) 2 wherein the OH group is ortho or para to the sulfur atom, the R substituents may be the same or different and are each alkyl radicals of 1 to 4 carbon atoms and n is an integer of 2 or 3.

2. A polyamide as claimed in claim 1 wherein there have been incorporated from 50 to 100 parts per million of said phosphorus.

13. A polyamide according to claim 1 wherein there have been incorporated from 400 to 1000 parts per'million of said sulphur-containing phenol.

4. A polyamide as claimed in claim 1 wherein' there have been incorporated from 400 to l000parts' per million of manganese as a light stabilizer. f

5. A polyamide as claimed in claim 1 wherein there have been incorporated from 10 to 100 parts per million of manganese as a light stabilizer.

6. A polyamide as claimed in claim 1 wherein hydroxyl groups of the sulphur-containing phenols are located symmetrically on benzene rings in the parapositions to the S atom. v r I 7. A polyamideas claimedin claim 1 wherein the sulphur-containing phenol is bis(2-methyl-4-hydroxy-5-tbutyl phenyl) sulphide.

8. A polyamide as claimed in claim 1 wherein said polyamide is polyhexamethylene adipamide, with or without added pigment.

9. Fibres, filaments, yarns, fibres, fabrics and other textile materials shaped from polyamides as claimed in claim 1.

References Cited UNITED STATES PATENTS 2,493,597 1/1950 Rothrock et al. 260-45. 7 2,510,777 6/1950 Gray 260-] 2,630,421 3/ 1953 Stamatofi 260-45] 3,026,264 3/1962 Rocklin 260-4595 3,086,960 4/1963 Bletso 260-4595 3,196,185 7/1965 Ranson 260- 4595 3,324,071 6/1967 Skoog 260-37 DONALD E. CZAJ A, Primary Examiner V. P. HOKE, Assistant Examiner US. Cl. X.R.

260-37 N, 45.7 P, 45.9 R, 45.95 R 

